Question

câu 1: thực hiện phép tính: a)\(\dfrac{8}{5}-\dfrac{9}{5}\) ; b)\(\dfrac{5}{2}+\dfrac{2}{3}\) ; c)\(\dfrac{-5}{9}.\dfrac{2}{11}\); d)\(\dfrac{-2}{9}:\dfrac{1}{3}\); e)\(\dfrac{3}{8}+\dfrac{-1}{4}+\dfrac{5}{12}\); f)\(\dfrac{-4}{3}.\dfrac{5}{4}:\dfrac{7}{3}\)

Answer 1

a) \(\dfrac{8}{5}-\dfrac{9}{5}=\dfrac{8-9}{5}=\dfrac{-1}{5}\)

b) \(\dfrac{5}{2}+\dfrac{2}{3}=\dfrac{15}{6}+\dfrac{4}{6}=\dfrac{15+4}{6}=\dfrac{19}{6}\)

c) \(\dfrac{-5}{9}\cdot\dfrac{2}{11}=\dfrac{-5\cdot2}{9\cdot11}=\dfrac{-10}{99}\)

d) \(\dfrac{-2}{9}:\dfrac{1}{3}=\dfrac{-2}{9}\cdot3=\dfrac{-2}{3}\)

e) \(\dfrac{3}{8}-\dfrac{1}{4}+\dfrac{5}{12}=\dfrac{9}{24}-\dfrac{6}{24}+\dfrac{10}{24}=\dfrac{9-6+10}{24}=\dfrac{13}{24}\)

f) \(\dfrac{-4}{3}\cdot\dfrac{5}{4}:\dfrac{7}{3}=\dfrac{-4}{3}\cdot\dfrac{5}{4}\cdot\dfrac{3}{7}=\dfrac{-4\cdot5\cdot3}{3\cdot4\cdot7}=\dfrac{-5}{7}\)